Dear all,

As a postscript to Steve's comments, I ordered a similar 2.5 purity tank of
CO from Praxair, but it turned out to have a very light composition.  I
received my CO from a Las Vegas distribution centre, so it's almost
certainly a different lot number.  Hence, by ordering CO in the US, you
might get lucky, and then again, you might not!

Cheers,
Simon



>     For what it's worth, we recently received a EuroVector EA and needed
>some CO quickly in order to set it up and test it for oxygen pyrolysis.
>The only thing we could come up with quickly was a 2.5 purity tank from
>Praxair.  To our surprise it had a very low background for water and O2 and
>not much of anything else showed up in the background scans.  In addition,
>it turned out to have a very workable d18O value of around +17 per mil.
>The delta value is just a rough estimate based on the value we get for our
>nitrate oxygen standard but it's certainly not off by hundreds of per mil.
>I have no idea if lower purity CO normally has such a workable oxygen
>composition or we were just lucky.  If it's the rule rather than the
>exception, maybe lower purity CO could be scrubbed for contaminants in the
>lab.  The Micromass engineer who installed our instrument  thought he
>remembered someone else having the same experience.
>
>Steven Silva
>U.S. Geological Survey

*****
Simon R. Poulson
Dept. of Geological Sciences, MS-172
University of Nevada-Reno
Reno, NV 89557-0138
USA
Phone: (775) 784-1104
Fax: (775) 784-1833
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*****